Vacuum distillation



May 12, 1931. w. B. LGAN 1,804,941

K VACUUM DISTILLATION Filed Dec. 2'7, 1927 5H ROMETR/C CONDE/VSE?? FUE/wv CE 50 top of the Patented May 12, 1931 OF NEW Yoan,

Applicationjled December 27;

This invention relates to vacuum distillation and more particularly to a process for the distillation of mineral lubricating oils under vacuum.'V In its broadest aspect the invention comprises a lprocess wherein mineralo lubricating oil is vaporized in a still, after which the heated vapors pass into a friction-J ating tower where the`y are condensed, wholly or in part, by means of cooling supplied through the direct introduction of water into the'oilvapors, the entire process being conducted under sub-atmospheric pressure.

The invention may be readily understood from a description of the l process considered in connection with the accompanying drawing which represents in diagrammatic sectional elevation an appara- Atus which maybe employed for carrying on the process. The apparatus illustrated in the drawing is shown and described merely for the purposeof yaiding and understanding the process and lit is to bev understoodjthat any other suitable apparatus may be substituted for that shown. Referring to the drawing, there is provided a heating coil 11 for the purpose of heatingy the oil to .be distilled, the coil being place/d in a suitable furnace 12. Connected to the coil by the flow line 13, fitted with the 3o valve 14, is a still 15a-which is placed in. a suitable furnace (not shown). A suitable means is provided for introducing steam into the still below the level ofthe liquid contained therein, as the perforated pipe 30a. The still is connected by means of the vapor line 16al to the fractionating tower 17a provided with suitable baiiles as shown. From the bottom ofy the 26a is provided, passing through the cooling coil 27 a to which the pump 28a connects and discharges to the storage tank 29a. From the top of the tower 17 a a vapor line 18a is provided passing to the barometric condenser 19a. 1

A water line 20 from a suitable source supplies water to the barometric condenser 19a',

through the connection 21a and also to theA upper portion of the tower 17 a through the connection 22a` and the spray 23a. From the barometric' condenser-a line 24a 11l cUUM nIs'rrLLA'VrIoN procedure of the.

towerj17a a connection` cury. Distillation of the oil takes place withthrough the perforated pipe 30a. The oil xAs, AssreNoa ro 'rmx 'rms N. Y., A eoarom'rron or DnLAwm I 1927. seriaiNo. 242,651.

isv connected to a dry vacuum pump 25. The

water supplied tothe barometric condenser- `19a is discharged together with any condensate entering the condenser through the connection 18a, through .the line 35a to a' 55 suitable hot-well (not shown) which may ,be

fitted with means Afor separating oil and water. I lAn overflow line 31a providesa means for the contents of the still 15a to overflow intoV the next still of the series-15b. In the apparatus as illustratedV only two stills are shown connected in series but any, number of stills might be used, depending up'onthe number of fractions which it is desired to obtain. The still 15bA with its corresponding tower, barometric condenser, water connections, etc. f

lis a substantial counterpart of the still 15a and its connected tower, barometric condens- From the still15b, which in the present instance is'the last stillof the series, the overflow line 3lb-is connected to the pump 33 through .the cooling coil 32, the pump discharginglinto the residuum container 34'.

The operation of the process in connection with the apparatus shown may be as follows: A suitable chargingl stock, for example an intermediatecut obtained from a Gulf Coastal crude petroleum, is supplied from a source (not shown) to the heatingcoil wherein it 80 may be heated to the temperature desired, say for example 600 F Q The oil in the heating coil ismaintained at pressures equal to atmospheric or above. The valve 14 is partially opened allowing the oil from the heating coil to be continuously drawn into the still 15a, which is maintained nder a' pressure less than atmospheric, preferably under an absolute pressure of about 25-'50 mm. of merno in the still lw and the degree of distillation maybe controlled both by the addition of heat i to the still and also'by the introduction of a carefully regulated' quantity of steam yvapors evolved from the still consist chiefly of lubr1cat1ng` oil fractions' and ythese pass from the still through the vapor line 16a to .the fractionating tower 17 a.

" In'pthe apparatus described for the purpose 10 of illustrating the invention, the fractionating tower has been illustrated as a simple baille tower. However, it will be understood that other suitable types of towers, such for example as packed towers or bubble towers, may be used, the type oftower depending in general u pon the degree of fractionation which it is desired to accomplish. In the present instance in which'the distillation of an intermediatevfraction of a Gulf Coastal crude is contemplated, close fractionation of the various cuts is not required and accordingly the comparatively ineicient but inexv pensive-'bathe tower .serves the desired purpose. l

The vapors entering the lower portion of the baille tower pass upward where they come in contact withl a spray of water introduced through the connection 22a and the distributer 23a. The temperature maintained 'n the tower is such that the water is accordingly vaporiz'ed, thereby abstracting heat from the oil vapors which are thus condensed and drop down through the tower. By the regulation of the quantity of water introduced through the connection 22a substantially any proportion of the oil vapors may be condensed in the tower 17 a.

AThe steam which was introduced into the still 15a passes'on through the tower 17 a and out through the line 18a together with the steam generated from the water introduced through the connection 22a.-

in the .preceding paragraph, the steam may carry with itacertain quantity of oil vapors,

depending in general upon the degree of cool- -ing applied to vthetop of the tower by the introduction ofa controlled amount of water 21a and is condensed,

through the connection 22a. The steam passing through the line 18a enters the barometric condenser 19a where it comes in contact with cool water introduced through the connection thus producing a vacuum both on the tower 17a and the still 15a. The water from the barometric condenser vis dischar ed through the line 35a'to a suitable hot-we system.`

The oil condensed in the tower 17 a collects in'the lower section from which it flows b gravity through the line 26a and the cooling 27a, from which it is forced by means of the pump 28a, to a storage tank 29a,'main tained undery normal atmospheric pressure.

As shownV inthe drawing,a second still 15b is provided which is substantially a counterpart of the still 15a but which normally will be maintained at a higher, temperature than 15a. Undistilled oild from the still 15a over flows through the. line 31a-into the still 15b where it undergoes further distillation at a higher'temperature, the fractions thus distilled off being heavier and more viscous than those distille from the still 15a. The operationof the Still 15b is in general substantially the same as that described for the still As pointed outA y not only darken the color but terjrequired to be supplie to the top of the tower,17Z s shown in the drawing, the still 15b represents the last still in the series of stills. It was mentioned in a previous paragraph that any desired number of stills may be employed in the series. From the last still in the series, in this instance still 15b, the -undistilled residuum overflowsby way of the line 316, through the cooling coil 32, from which it is forced by means of a pump 33 to a suitable storage receptacle 34, maintained under normal atmospheric pressure. Y

The cooling of the upper portion ofthe fractionating tower by means of the direct introduction of water therein is of particular `importance' in connection with the vacuum distillation of mineral lubricating oils and the employment of this procedure results in the economical production ofthe 'highest grades of distillate lubricating oils. In the case of ordinary `distillation under normal atmospheric pressure, other means of cooling might readily be employed. For example, a cool fluid might be circulated through suitable pipe .coils in the upper portion of the tower, the fluid never coming directly in contact with the oil vapors. However,l in the case of vacuum distillation, such an arrangement is not practical as the rarified condition of the vapors would maire necessary the 4use of an enormous pipe surface, so great -in fact as to be impractical. On the other hand, the more or less usual cooling to the top` of a fractionating tower during the distillation of lighter oils such as gasoline, that is, the direct introduction of cool oil,is not practical where it is necessary to produce highly purified and stable lubri cating oil distillates. Thus, if cool lubricating'o'il, or any other oil, were introduced into the top of the towers 17 a, 17 b, etc., all of the cooling-oil would not be evaporated and portions of this oil would be subjected to enough heat and over a sufficient period of time to produce impurities which would destroy other desirable properties of the oil, such for example,

vapors from the still thereby contaminating them to an undesirable extent.- The cooling of the towers by the direct introduction of water has none of these disadvantages and, in the vacuum distillation of mineral lubricating oil, it lis by this means alone that a product may be economically ob-p method of applying f as resistance to emulsiication. Such oil would then` be collected with condensed only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. The process of distilling mineral lubrieating oil which comprises continuously vaporizing the oil under an absolute pressure not exceeding 25-50 mm. of mercury, passing evolved vapors into a tow r, introducing water into the upper ortion of the tower 10 whereby a portion o said vapors arecondensed and the water evaporated, Withdrawing steam and oil vapors from the upper portion of the tower and withdrawing condensate comprising the desired lubricating oil from the lower portion of the tower.

2. The process of' distilling hydrocarbon lubricating oil which comprises vaporizing the oil in a still in the presence of steam, passing the oil vapors into a tower introducing water into the upper portion of the tower whereby a portion of said vapors is condensed and the water evaporated, withdrawing steam and oil vapors from the upper portion of the tower, and -withdrawing condensate comprising the desired lubricating oil from the lower portion of the tower, the process being carried on under an absolute pressure not exceeding 25-50 mm. of mercury.

3. The continuous process of distilling hydrocarbon lubricating oil which comprises continuously introducing the oil into a heated still wherein vaporization takes place, passing the oil vapors into a tower, introducing water directly into the upper portion thereof whereby a major portion-of said vapors is condensed and the water evaporated, withdrawing steam and a relatively4 small quantity of oil vapor from the upper portion of the tower, and withdrawing and collecting the condensate comprising the desired lubricating oil from the lower portion of the tower, the process being carried on under an absolute pressure not exceeding 25-50 mm. of

mercury.

In witness whereof I have hereunto set my hand this 7th day of December, 1927.

' WUJLIAM B. LOGAN. 

